1. Field of the Invention
The invention relates to the field of micromachined gyroscopes, in particular gyroscope designs with 2-DOF (two degrees of freedom) sense modes allowing interchangeable operation in either precision or robust modes.
2. Description of the Prior Art
Micromachined vibratory gyroscopes operate based on the Coriolis effect where a rotation induced energy transfer occurs between two orthogonal vibrational modes, commonly referred to as drive and sense. Conventionally, these modes are realized as single degree of freedom (DOF) dynamic systems with their own associated resonant frequencies giving rise to two differing methods of operation: mode-matched or mismatched. In mode-matched devices, the drive and sense resonant frequencies are equal allowing the output of the sensor to be increased proportional to the sense mode quality factor, thereby yielding higher sensitivities at the cost of reduced bandwidth and robustness. Operation with the resonant frequencies separated by some prescribed amount, or mode-mismatched, is more common, particularly for automotive applications where robustness is critical.
Previously, gyroscope designs have been introduced aimed at robust operation using an expanded sense-mode design space through increased degrees of freedom. Specifically, these devices use two coupled sense masses forming a 2-DOF dynamic system with two sense mode resonant frequencies and a wide region of constant amplitude between them. While the gain and the bandwidth of this operational region is controlled solely by the resonant frequency spacing, a constraint limited the minimal achievable spacing as the operational frequency of device with fixed size was increased. This is a direct effect of the dynamic vibration absorber type 2-DOF design, which utilized only two suspensions thereby eliminating the ability to independently define the frequency spacing and the coupling between the masses. In contrast, a complete 2-DOF system consisting of two masses and three suspensions alleviates this issue allowing for the arbitrary specification of frequency spacing independent of operational frequency.
What is needed is a interchangeable micromachined gyroscope that allows for both increased sensitivity and wide-bandwidth, robust operation in a single device.